Advice on RV Set up & Wiring?

[sensij]

Question: If I get more panel wattage than this it woulds just be a waste as it won't charge the batteries any faster based on a 30A max charge rate, it would just be excess capacity I could use for other things BUT based on my usage calculations above I only need 125W of panels to power the fridge so 330W should be more than enough to run my fridge set up and keep the batteries charged ???

Please edit your posts to show the distinction between Wh (energy) and W (power).

Use a Kill-a-watt to verify the fridge's consumption, and build in a fudge factor for seasonal variation. It is worth the $20 it costs.

Use PVwatts to get a better idea of seasonal array production (especially at the expected mounting orientation). Drill into the hourly output results. I'd set the loss at around 10%, and focus on the DC power and energy production. System loss calculations for battery based systems are different than for the grid-tie systems for which PVWatts is designed.

If your consumption is truly 624 Wh, I'd use 0.75 round trip efficiency on the battery, meaning you'd need to be capable of generating 832 Wh of charge daily. Another 10% loss on charge controller efficiency puts you at 924 Wh of generation from a solar panel... probably closer to 200 W of PV required than the 125 W you calculated.

With a 220 Ah battery, you really should try to get at least 18 amps into it routinely. I'd be looking for a deal on a 60 cell grid tie panel in the 250-300 W range, and a 30 A mppt CC. A 2nd panel would be excess capacity for future loads, as you say, but will help get your batteries through absorb into float more regularly, if you have space to mount it.

[Sunking]

Did you try reading the STICKIES? Here are a few examples of the proper wiring of an RV system.

[Carv]

Thanks Sensij -I have a kill a watt on the way but I wanted to run my calcs and see how close the two where (I think they'll be pretty close but testing will decide). I also realized I ran my Wh incorrectly and it should be 1,040Wh based on a 1/3 run time. So based on your loss formula above it comes out closer to 1,459Wh and based on a 5 area factor it leaves me at 291.93PVw

Based on your estimations and fudge factors with the 1,459Wh/ 292PVw, if I had a 330W panel, the panel would need 4.42 hours of full sun to run the fridge and charge the batteries? And if I had 2 -330PVw panels it would take 2.21 Hours of full sun?

If I placed 2 panels, it would require a 60A Controller (660Pvw/12V= 55A) BUT my batteries can only handle 30A charge based on their Ah & charge rate factors so if I limited the 60A CC output to 30A what would be the performance differences between the single panel at 330PVw VS. 2 -330PVW panels with the 30A limited CC?


Also I assume it probably gets more complicated too over the 24 cycle as I will be starting out day 1 with full batteries, so I only need to serve my daytime draw of (729Wh) BUT day 2 & after I will need to charge the batteries from the previous nights draw of 729Wh/12V = 60.72Ah AND serve my day time needs so the system is charges the batteries full to get it through the next night 6PM - 6AM.

Also I assume it's ok to run a 72 cell grid ties as well as the 60 cell as long as if I run 2 that I run the same exact ones?

Thanks



YES Sun King I've read your stuff and I have your diagrams downloaded but the diagrams you've posted do not answer my questions for my particular set up as I posted previously in this thread. Not everything people want to do will conform to how you think it should be built.

[Sunking]

Safety is not debatable. Fuse placement and size of circuit conductors is paramount to safe and proper operation. Only thing that changes is the component sizes like panel wattage, controller, battery, fuses, and wire sizes. They layout does not change.

Here is detailed answers to your questions.

Design

A1. 1 orr 2 panels is not the right form of the question. With off-grid battery systems you want to use standard size panels that fit to a controllers needs. Example using a 300 watt panel with a 15 amp MPPT controller does not work with 12 volts nor does it work good with 24 volt battery. A 15 amp controller limit is 200 watts @ 12 volt battery and 400 watts @ 24 volt battery. Just does not work. You want to stick with a very common 200 or 250 watt panel. Most all decent charge controllers work in increments of 10 amps like 30, 45, 60, and 80 amps. In an RV operating at 12 volts means wattage limit respectively is 400, 600, 800, and 1000 watts. Common denominator is 200 watt panels. 200 watt panels are very common 60 cell modules and specs are very close from one manufacture to another. So when it comes time to expand, a good chance your manufacture is bankrupt and you can use another manufacture panels. The other thing to avoid like the plague is using a prime number of panels except 1 and 3. With Prime numbers only leaves you two configurations of all in parallel, or all in series. Last thing you ever want is being forced to wire your panels in parallel.

A2. You do not want to use 315 watt panels. They are a square peg in a round holes as already explained. Sure you could use a 315 watt panel on a 30 amp controller, but that is it, you are done. A 30 amp MPPT controller can use up to 400 watts input. You just screwed yourself out of 85 watts of expansion. See answer 1.

A3. Cannot be answered directly. Depends on how deep the batteries are discharged, and what size the batteries are. In a properly designed system, it is not something you have to worry about. Use at least 4-day reserve capacity with a C/10 charge current and all that takes care of itself. In any battery system requires a generator anyway. That is why you want to use a Battery Isolator in an RV so the engine alternator does the bulk of the charging. Panels are for show and tell basically. You are going to need generator or Isolator. One hour driving will generate more energy than 2 days of sun on a 200 watt panel.

A3. Fully charged batteries do not take any current. Once the batteries have charged up and reach Float Stage, all current stops. From that point any power demand will come from the panels assuming the power demand does snot exceed what the panels can provide. Otherwise the batteries will make up the difference.

Wiring Questions

A1. The drawings I provided you answers your question in very specific detail. You can use distribution blocks on the Battery as shown if you feed DC power to other gizmos other then the Inverter. As for the Charge Controller to Battery, there is NO DISTRIBUTION nor can there be any. It is a dedicated run with a dedicated fuse as shown. The only thing that changes is the wire and fuse size and that depends on what size the controller is. See chart below chart for proper wire sizing with fuse. Use the 3% colomb. Again no debate here, it is CODE and Safety.

A2. No sir. You only bond the the negative battery term post once and only once as shown in the drawings. Otherwise if you bond it more than once, you put the vehicle frame in parallel with the negative circuit conductor, and that is a big NO-NO because you are now running normal load current through the vehicle frame. The bond is only there to operate the fuses and the only time current is allowed to use ground. Again look at the drawings I provided you. Now the CHASSIS of the Controller and Inverter can and should be be bonded to the frame and use a conductor as short as possible of the appropriate size based on the Fuse. Make life simple, if the largest conductor used in the system is 4 AWG, use 4 AWG for all bonding conductors.

A3. Incorrect. GFCI requires no ground to operate. The reason for the Chassis ground on the Inverter is for DC protection in the event the DC Positive conductor were to make contact with the chassis of the Inverter. Has nothing to do with the AC side. Most Inverters use a 15 or 20 amp GFCI Breaker. It takes 90 to 120 amps to operate a 15 and 20 amp respectively. A 2000 wat Inverter is only capable of generating 18 amps. The breaker is worthless because the Inverter cannot generate enough current to operate it. That is why all Mobile Inverters do not require a Ground and use a GFCI as it only take 0.1 amps to operate.

You may think my way does not fit your needs, it fits everyone's needs based on sound and safe design principles. Not only will it save your life and property, it will also make your system work at optimum design level intended. No one here will go to this level of detail to help you to do the job correctly and explain why it is done the way it is. FWIW it is not MY Way, it is industry practice, not done by some shade tree mechanic.

[sensij]

I'll look at your other questions later, but some quick responses

If I placed 2 panels, it would require a 60A Controller (660Pvw/12V= 55A) BUT my batteries can only handle 30A charge based on their Ah & charge rate factors so if I limited the 60A CC output to 30A what would be the performance differences between the single panel at 330PVw VS. 2 -330PVW panels with the 30A limited CC?

Sunking and I clearly disagree on this. Unless you plan to expand the system someday, I wouldn't buy a 60 A cc. Just buy the 30 A CC. Even if you over-panel it, it will self limit to 30 A output. By adding the 2nd panel, you won't double the energy output you had gotten from just one, but you substantially increase the number of hours you are capable of delivering the 30 A that the battery wants to see. Sunking says "you are wasting panel power" I say "you are taking better care of your battery, for only the incremental cost of a panel"

I'll try to post some charts later that illustrate this.

Also I assume it's ok to run a 72 cell grid ties as well as the 60 cell as long as if I run 2 that I run the same exact ones?

Be careful with this. 12/24 V mppt controllers appropriate for RV's are usually limited to 100 Voc max. With standard 72 cell panels in series, if you ever have temps approaching freezing, you might go over that limit. With highly efficient 72 cell panels, your safe temperature range is even narrower.

Edit: In parallel, all you have to do is match the voltage, so almost any pair of 72 cell panels will get along. It can be limiting though... Adding a third in parallel gets more complicated.

[Wrybread]

Small note:

> if I get 1 panel at 330W it should generate 27.5A at the charge controller

The real world output of your panels won't be anything near that most of the time, *especially* if you're flat mounting them. I've got two flat mounted 310 watt panels and the most power I've ever gotten from them is 475 watts, meaning about 237 watts each. Usually less than that. That said, I've only had them in winter and spring, and in Northern California. But I wouldn't plan your system based on the peak output of your panels. And as Sensij says, even if your panels are putting out more power than your charge controller is rated for, it will self limit to it's rated output. At least all the MPPT charge controllers I've seen will, but you should confirm that any model you're buying does the same.

[Carv]

My post keeps getting cut off, I preview it and it's fine I save it and over half of it's gone, anybody (admin) got an idea why?

[sensij]

When you cut and paste, some characters aren't accepted and cause the forum software to terminate the post. I run into trouble with apostrophes, quotation marks, dashes, and other less common characters. Look for where the termination is happening and retype that character in the forum window, instead of pasting it.

[Sunking]

Sunking and I clearly disagree on this. Unless you plan to expand the system someday, I wouldn't buy a 60 A cc. Just buy the 30 A CC. Even if you over-panel it, it will self limit to 30 A output.

Sensij I have no problem with a smaller 30 amp controller. He should buy one with expansion in mind. On an RV makes no sense to over panel a controller. For that matter makes no sense on a stationary system either. It is all about smart planning. 300 watt panels building blocks do not work well with 12 and 24 volt controllers as their Voc limit is usually 100 Voc or less. If you use 300+ watt panels are 72-cell panels limits you to a maximum of 2 panels in series, and in cold climates just 1 in series, plus wasted power. Parallel arrangements get expensive with more wire, combiners, and fusses if needed. It just does not make any sense to do that especially on an RV where you should have a battery isolator to do the heavy charging. A good Isolator cost $50 and a much wiser investment than throwing money away on a panel you cannot utilize the full potential.

200 watt panels are the perfect building blocks and will work with any Controller Input limits. Not to mention any 200 watt 60-cell panel specs are the same from any manufacture. They all have a Voc of roughly 36 volts and Imp of 7 amps from any manufacturer, and CHEAP. Save the wasted money to buy an Isolator or generator which is required anyway. It is just smart design and money. .

There is a method to my madness. Makes no sense to pound an expensive square peg in a cheap round hole. When you over power a MPPT controller and force it into limiting generates higher than normal heat stress on the Controller.

[Carv]

Sunking and I clearly disagree on this.

Well youre not the only one... he seems to have a lot of knowledge and I appreciate his advice, it just seems to be very ethereal in nature and does not take in to account for your particular situation. In the real world there are other considerations, physical limitations, & cost factors that come in to play. For example 1 VS 2 panels is not necessarily the main question but it does make a major difference in MY situation and knowing what the cost VS benefit of 1 VS. 2 is would help me make a decision as to what sacrifices Im willing to accept in exchange for what benefits I receive and how they apply to MY situation.

For example; these panels are going on my trailer roof and 2 panels is twice the pain in the A$$ as 1 to mount. two take up twice the room and prevents me from mounting an overhead AC in the future (makes me alter other plans with additional cost, location, & wiring considerations), plus I have to build 2 tilt kits, and mount them in a way where I can tilt them both ways without getting on the roof, PLUS I need access to wash & wax the roof under where the panels would be mounted again without stepping on the roof, etc.

SO....please no pontification (of theory) without consideration (of the actual situation). Its great for flexing your knowledge but without consideration of the particular situation (which Ive done my best to highly detail in this post) theoretical recommendations that ignore my specific situation & questions do not help me because as you can see in the real world of application there are MANY other things to consider. This is why most people including myself are here asking questions so they/I can understand and make an educated decision as to what is best for them and their situation (me included).

Unless you plan to expand the system someday, I wouldnt buy a 60 A cc. Just buy the 30 A CC. Even if you over-panel it, it will self limit to 30 A output. By adding the 2nd panel, you wont double the energy output you had gotten from just one, but you substantially increase the number of hours you are capable of delivering the 30 A that the battery wants to see. Sunking says "you are wasting panel power" I say "you are taking better care of your battery, for only the incremental cost of a panel"

Ill try to post some charts later that illustrate this.

Thanks I was thinking that was the benefit, as 30A is 30A, the more panels would just expand the time I can deliver 30A.

Be careful with this. 12/24 V mppt controllers appropriate for RVs are usually limited to 100 Voc max. With standard 72 cell panels, if you ever have temps approaching freezing, you might go over that limit. With highly efficient 72 cell panels, your safe temperature range is even narrower.

I never experience temps lower than 45-50 when the sun is up, It can get to 20s at night and the first 90 minutes of day break so not sure how that plays in to it (again that dang real world making problems)?
So 60 cell panels have a lower Voc rating and can handle a wider range of temperatures than 72 cells without pushing over the Max Voc of the charge controller?

Im probably looking at a morning star MPPT TS 45, do you know what their Voc max is?

Thanks for the help

Sensij I have no problem with a smaller 30 amp controller. He should buy one with expansion in mind. On an RV makes no sense to over panel a controller. For that matter makes no sense on a stationary system either. It is all about smart planning. 300 watt panels building blocks do not work well with 12 and 24 volt controllers as their Voc limit is usually 100 Voc or less. If you use 300+ watt panels are 72-cell panels limits you to a maximum of 2 panels in series, and in cold climates just 1 in series, plus wasted power. Parallel arrangements get expensive with more wire, combiners, and fusses if needed. It just does not make any sense to do that especially on an RV where you should have a battery isolator to do the heavy charging. A good Isolator cost $50 and a much wiser investment than throwing money away on a panel you cannot utilize the full potential.

200 watt panels are the perfect building blocks and will work with any Controller Input limits. Not to mention any 200 watt 60-cell panel specs are the same from any manufacture. They all have a Voc of roughly 36 volts and Imp of 7 amps from any manufacturer, and CHEAP. Save the wasted money to buy an Isolator or generator which is required anyway. It is just smart design and money. .

There is a method to my madness. Makes no sense to pound an expensive square peg in a cheap round hole. When you over power a MPPT controller and force it into limiting generates higher than normal heat stress on the Controller.

Now that is some real world information, so two 225PVw 60 cell panels would be better than 1 330PVw panel for avoiding hitting the CC Voc rating limits?

If I did 2 225W panels itd generate 37.5A and my batteries at a C/8 are 27A charge/discharge rate, so If I limited the charging amps on the controller to 30A, what would be the difference between a single 330W and 2 225W panels, just the amount of time I can supply the 30A?

Thanks

[Sunking]

Well youre not the only one... he seems to have a lot of knowledge and I appreciate his advice, it just seems to be very ethereal in nature and does not take in to account for your particular situation. In the real world there are other considerations, physical limitations, & cost factors that come in to play. For example 1 VS 2 panels is not necessarily the main question but it does make a major difference in MY situation and knowing what the cost VS benefit of 1 VS. 2 is would help me make a decision as to what sacrifices Im willing to accept in exchange for what benefits I receive and how they apply to MY situation.

For example; these panels are going on my trailer roof and 2 panels is twice the pain in the A$$ as 1 to mount. two take up twice the room and prevents me from mounting an overhead AC in the future (makes me alter other plans with additional cost, location, & wiring considerations), plus I have to build 2 tilt kits, and mount them in a way where I can tilt them both ways without getting on the roof, PLUS I need access to wash & wax the roof under where the panels would be mounted again without stepping on the roof, etc.

My design POV is based on priorities in the following order.

1. Safety. I am a professional engineer and public safety is my priority. I am liable for all my designs.
2. Functional and meets the objective..
3. Economics. Do your homework on me, I can save you hundreds of dollars.

As for room, 3 x 200 watt panels use the exact same amount of room as 2 x 300 watt panels made from the same PV cells. That is just a fact. A PV panel with 20% efficiency means 1 square meter will be 200 watts. Makes no difference how you slice or dice it. 600 watts is going to take up 3 square meters of area.

SO....please no pontification (of theory) without consideration (of the actual situation). Its great for flexing your knowledge but without consideration of the particular situation (which Ive done my best to highly detail in this post) theoretical recommendations that ignore my specific situation & questions do not help me because as you can see in the real world of application there are MANY other things to consider. This is why most people including myself are here asking questions so they/I can understand and make an educated decision as to what is best for them and their situation (me included).

I explained ever answer and why. So what is the problem?

Now that is some real world information, so two 225PVw 60 cell panels would be better than 1 330PVw panel for avoiding hitting the CC Voc rating limits?

Depends on the Controller Voc limit and current rating. Without a doubt two 225 watt panels is better if the controller Voc is 100 volts or less. With 60-cell panels you can series connect them, and that means less expensive because you can use less and smaller wire. See my economics are included in my answer. Secondly answer this question. Which panel has the most watts. A single 330 watt panel or two 225 watt (450 watts) panels?

Stupid question right? Who is buried in Grant's tomb?

If I did 2 225W panels itd generate 37.5A and my batteries at a C/8 are 27A charge/discharge rate, so If I limited the charging amps on the controller to 30A, what would be the difference between a single 330W and 2 225W panels, just the amount of time I can supply the 30A?

You are taking things to deliberate. As a generic rule, FLA batteries need at least a C/12 charge current to prevent Stratification, and no more than C/8 to prevent over heating. The minimum C/12 is a solid answer, However the max C/8 charge rate is not written in stone. It has to do with the batteries Internal Resistance that limits the maximum charge and discharge rate. It is cautious safe answer I can sleep with. However all FLA batteries are not the same. Example SLI aks Starting or Cranking batteries can be charged and discharged a rates exceeding 1C. That is why when you see a 12-volt starting battery may only have 60 AH but can supply 800 amps CCA and CA. That would be roughly 13C.

In an RV a hybrid battery is often the default choice to use because of the gawd awful oversized 12 volt Inverter. Example a 12 volt 1000 watt Inverter requires 100 amps of current. If you used a True Deep Cycle Battery means you would need a 800 AH battery. You do not have the room or can afford that much weight. This is where hybrid batteries like a Golf Cart battery come into play, or very expensive AGM batteries. They have much lower Internal Resistance, thus can deliver much higher discharge currents and much higher charge currents. Example a Trojan T-105 has an Internal Resistance of .003 Ohm's, and thus two in series would be .006 Ohms. On the charge side heating is the limiting factor and for any Pb battery you want to limit thermal capacity to 0.05 watt per AH. Bet no one here even knows that limit. So if we use a single cell Ri = .001 Ohms and the max thermal charge limit is the square root of [ .05 x 225] / .001 = 106 amps thermal limit.

Now on the discharge side you want to limit the rate to no greater than 5% voltage drop. 5% of 12 volts = .6 volts. So max discharge rate is ,6 volts / .012 Ohms = 50 amps. So for a Trojan T-105 you can charge as high as C/2, and discharge up to C/4 without issues of over heating or performance degradation.

[Carv]

Safety is not debatable. Fuse placement and size of circuit conductors is paramount to safe and proper operation. Only thing that changes is the component sizes like panel wattage, controller, battery, fuses, and wire sizes. They layout does not change.

Here is detailed answers to your questions.

Design

A1. 1 orr 2 panels is not the right form of the question. With off-grid battery systems you want to use standard size panels that fit to a controllers needs. Example using a 300 watt panel with a 15 amp MPPT controller does not work with 12 volts nor does it work good with 24 volt battery. A 15 amp controller limit is 200 watts @ 12 volt battery and 400 watts @ 24 volt battery. Just does not work. You want to stick with a very common 200 or 250 watt panel. Most all decent charge controllers work in increments of 10 amps like 30, 45, 60, and 80 amps. In an RV operating at 12 volts means wattage limit respectively is 400, 600, 800, and 1000 watts. Common denominator is 200 watt panels. 200 watt panels are very common 60 cell modules and specs are very close from one manufacture to another. So when it comes time to expand, a good chance your manufacture is bankrupt and you can use another manufacture panels. The other thing to avoid like the plague is using a prime number of panels except 1 and 3. With Prime numbers only leaves you two configurations of all in parallel, or all in series. Last thing you ever want is being forced to wire your panels in parallel.

-I'm using 12V, my original post noted this & why

A3. Cannot be answered directly. Depends on how deep the batteries are discharged, and what size the batteries are. In a properly designed system, it is not something you have to worry about. Use at least 4-day reserve capacity with a C/10 charge current and all that takes care of itself. In any battery system requires a generator anyway. That is why you want to use a Battery Isolator in an RV so the engine alternator does the bulk of the charging. Panels are for show and tell basically. You are going to need generator or Isolator. One hour driving will generate more energy than 2 days of sun on a 200 watt panel.

-I provided the estimated usage in Wh and my battery set up in the previous posts, as well as the fact that I do have a generator and that I will be starting with full charge batteries (no need for an isolator).

Wiring Questions

A1. As for the Charge Controller to Battery, there is NO DISTRIBUTION nor can there be any. It is a dedicated run with a dedicated fuse as shown.

-As I explained & asked in an earlier post, Since the CC provides positive DC is there any reason it can not be tied in at the positive line from the battery instead of making a run back through the floor and back outside to the battery terminals, as I believe DC is non directional? (see attached diagram on 1st post)

A2. No sir. You only bond the the negative battery term post once and only once as shown in the drawings.

-I'm not looking to bond the negative battery terminal more than once I simply want to bond the negatives of the equipment at the mounting location instead of making another run back through the floor of the trailer to the negative battery terminal (according to how you've suggested, that would now be three runs through the floor back to the batteries which I'm trying to avoid). Again please see earlier posts and the diagram in my 1st post of how I'd like to run it.

A3. Incorrect. GFCI requires no ground to operate. The reason for the Chassis ground on the Inverter is for DC protection in the event the DC Positive conductor were to make contact with the chassis of the Inverter. Has nothing to do with the AC side. Most Inverters use a 15 or 20 amp GFCI Breaker. It takes 90 to 120 amps to operate a 15 and 20 amp respectively. A 2000 wat Inverter is only capable of generating 18 amps. The breaker is worthless because the Inverter cannot generate enough current to operate it. That is why all Mobile Inverters do not require a Ground and use a GFCI as it only take 0.1 amps to operate.

-Here are the grounding specs on the inverter where it talks about a bonded neutral on mobile applications per NEC, So back to my original question, if I ground the inverter chassis to the same spot as the inverters DC negative terminal will it create ground loop & trip the GCFI? Go Power Grounding Specs.jpg




I've tried to be as detailed as I can but it does me no good if the information I've provided is not taken in to consideration in your responses. Again I'm looking for the pretty specific answers as there seems to be an exorbitant amount of limitations when dealing with solar and each component seems to be limited by something else on another component.

Thanks

[Carv]

You are taking things wrong. As a generic rule, FLA batteries need at least a C/12 charge current to prevent Stratification, and no more than C/8 to prevent over heating. The minimum C/12 is a solid answer, However the max C/8 charge rate is not written in stone. It has to do with the batteries Internal Resistance that limits the maximum charge and discharge rate. It is cautious safe answer I can sleep with. However all FLA batteries are not the same. Example SLI aks Starting or Cranking batteries can be charged and discharged a rates exceeding 1C. That is why when you see a 12-volt starting battery may only have 60 AH but can supply 800 amps CCA and CA. That would be roughly 13C.

In an RV a hybrid battery is often the default choice to use because of the gawd awful oversized 12 volt Inverter. Example a 12 volt 1000 watt Inverter requires 100 amps of current. If you used a True Deep Cycle Battery means you would need a 800 AH battery. You do not have the room or can afford that much weight. This is where hybrid batteries like a Golf Cart battery come into play, or very expensive AGM batteries. They have much lower Internal Resistance, thus can deliver much higher discharge currents and much higher charge currents. Example a Trojan T-105 has an Internal Resistance of .003 Ohm's, and thus two in series would be .006 Ohms. On the charge side heating is the limiting factor and for any Pb battery you want to limit thermal capacity to 0.05 watt per AH. Bet no one here even knows that limit. So if we use a single cell Ri = .001 Ohms and the max thermal charge limit is the square root of [ .05 x 225] / .001 = 106 amps thermal limit.

Now on the discharge side you want to limit the rate to no greater than 5% voltage drop. 5% of 12 volts = .6 volts. So max discharge rate is ,6 volts / .012 Ohms = 50 amps. So for a Trojan T-105 you can charge as high as C/2, and discharge up to C/4 without issues of over heating or performance degradation.

Sun King you seem to know a lot but all the theoretical gobbly gook really does not help as there seems to be a flexible rule you refer to for every pontification you have. I tried to do my home work and I've read a bunch of posts including yours and it seems that the rules are always flexible depending on how you'd like to wax poetic or what situtation you'd like to use an an example. I got the C/8 charge rate from one of your post as you said it was safe for 6V GC batteries BUT now I should use a C/12 or a C/2 if I have trojan T105s BUT I don't have T105s I have centennial GC2200Ps AS I STATED PREVIOUSLY.

Your theory is great but please read my posts about what I have and what I'm looking to do BEFORE YOU REPLY as a bunch of book theory does not help answer my (or anybody eases) very specific questions.


So for example if you had said you 2 -6V G batteries are rated at 214Ah (Like I stated previously) at a charge rate of C/? as it seems to change depending on what situation you pick to refer to (not mine) would yield a acceptable charge rate of X on your system, that would help.

I've already laid out my system components that I have a what I need, please refer to the specific components I've listed in my previous posts as anything else does not help.

As for room, 3 x 200 watt panels use the exact same amount of room as 2 x 300 watt panels made from the same PV cells. That is just a fact. A PV panel with 20% efficiency means 1 square meter will be 200 watts. Makes no difference how you slice or dice it. 600 watts is going to take up 3 square meters of area.

P.S. in the real world 1 panel takes up half the room of 2, and 2 take up twice as much room as 1.

IF YOU REALLY WANT TO HELP PEOPLE, YOU REALLY NEED TO LISTEN TO THEM FIRST.



Now if someone else would be kind enough to chime in with an actual answer that'd be great.

1) so two 225PVw 60 cell panels would be better than 1 330PVw panel for avoiding hitting the CC Voc rating limits?

2) If I did 2 225W panels itd generate 37.5A and my batteries at a C/8 are 27A charge/discharge rate, so If I limited the charging amps on the controller to 30A, what would be the difference between a single 330W and 2 225W panels, just the amount of time I can supply the 30A?

Thanks in advance.

[Sunking]

-I'm using 12V, my original post noted this & why

What are you talking about? I know you are using 12 volts. What I am trying to tell you is Controllers made for strictly 12/24 volt battery system have a Voc Limit of 100 volts or less. Once you get up to 40 amps the charge controllers can be used for 12, 24, and 48 volt batteries with a Voc input of 150 volts to 600 volts. That makes it possible to wire all panels in series saving you a ton of money and and more efficient.

-I provided the estimated usage in Wh and my battery set up in the previous posts, as well as the fact that I do have a generator and that I will be starting with full charge batteries (no need for an isolator).

Trust me you are going to need and want one. If you drive everyday and have an Isolator, you can forget all about solar panels as you would have no use for them. The Isolator will top off the batteries every time you drive so when you park, you have fully charged batteries. Do as you please.

-As I explained & asked in an earlier post, Since the CC provides positive DC is there any reason it can not be tied in at the positive line from the battery instead of making a run back through the floor and back outside to the battery terminals, as I believe DC is non directional? (see attached diagram on 1st post)

Got news for you DC is directional. Current can only flow in one direction

-I'm not looking to bond the negative battery terminal more than once I simply want to bond the negatives of the equipment at the mounting location instead of making another run back through the floor of the trailer to the negative battery terminal (according to how you've suggested, that would now be three runs through the floor back to the batteries which I'm trying to avoid). Again please see earlier posts and the diagram in my 1st post of how I'd like to run it.

You are not looking at the drawings or understand what you see. There are only two cables connected to the positive battery term post, and 3 to the negative term post. On the positive post you have one conductor going to the Controller, and one going to the load. Each cable must be fused to protect the wiring and the fuses are connected directly to the battery post that protects each wire. There are only 2 wires period and no other options or shortcuts.

As for the Negative Battery Term post there are three required wires. One to the Controller, one to the load. Again no other options or short cuts.

-Here are the grounding specs on the inverter where it talks about a bonded neutral on mobile applications per NEC, So back to my original question, if I ground the inverter chassis to the sames pot as the inverters DC negative terminal will it create ground loop & trip the GCFI? Go Power Grounding Specs.jpg

You are talking non-sense NEC does not apply to vehicles. An Inverter is a Separately Derived Source which means there is no Galvanic connection between the DC Input and AC output. Input and output are electrically isolated. There are no ground loops. The chassis ground is for DC wire protection. The AC side is protected via the GFCI breaker.

I've tried to be as detailed as I can but it does me no good if the information I've provided is not taken in to consideration in your responses. Again I'm looking for the pretty specific answers as there seems to be an exorbitant amount of limitations when dealing with solar and each component seems to be limited by something else on another component.

I am giving you very specific detailed answer directly to your application. You just are not understanding the answers. Example you do not even understand what the document about Grounding is telling you.

[Wrybread]

Trust me you are going to need and want a generator

That's *highly* debatable. I've never once needed a generator in my RV, and I've been at it for 20+ years. Now the first thing I do when I get a new RV is rip the gennie out. Makes a great spot for battery storage by the way.

Unless you're using an air conditioner, there's absolutely zero need for a generator in my experience, especially if you're not living in the camper. Solar is your friend, especially in an RV.

And despite the recent turn in this thread, there's no need to over complicate it. As long as you're keeping it safe of course.